YET AGAIN Americans feel the special rush and check of emotion that comes from seeing a hostage return to the embraces and good wishes of his fellow citizens and then realizing that others are still in peril. The Rev. Lawrence Jenco of Catholic Relief Services in Beirut is free, 18 months after being kidnapped there. But three other Americans remain held by the group known as Islamic Holy War. Pictured smiling and waving an American flag, Mr. Jenco was described as having been released ''unharmed.'' Unharmed! The word mocks the abuse and pain that terrorists inflict by seizing, holding and intimidating innocents, even if they are then released with limbs intact and no open wounds. The word gives sadistic criminals, who here appear to have "executed" one American, William Buckley, an undeserved moral free pass. The truth is, Mr. Jenco was released alive but harmed, badly harmed, unforgivably harmed.

Americans owe much to Mr. Jenco and the others. Cast involuntarily in a pawn's role, they were snatched up to force an action by their government, in this case evidently to see to Kuwait's release of a group of convicted Shiite terrorists. The question for the United States is how to match its responsibility to these citizens with its responsibility to Kuwait, which is bravely holding out against a deadly terrorist threat, and with its responsibility to other Americans who could be at risk if the impression spread that you can get what you want in international life by grabbing a few Americans. On a tape that Mr. Jenco brought out with him, one American still detained pleaded for Washington to negotiate his and his comrades' release. The painful truth remains that the victims' claim for rescue undercuts any bargaining government's need to be able to show patience over the long haul.

Mr. Jenco was let go in an area of eastern Lebanon controlled by the Syrians, who are in at best an ambiguous position. Having recently been exposed in the West for plotting to blow up a loaded airliner in flight, the Syrians were pleased in this instance to show solicitude for victims of someone else's terrorism. But as long as Syria maintains its current close association with Iran, the patron of Islamic Holy War, it will be under pressure to coddle this murderous group. It is risky to speculate on what considerations guided Islamic Holy War, Iran and Syria, if they are the relevant parties, in freeing Mr. Jenco. Perhaps it is impolitic to ask the Syrians in particular why they did not see to the release of Mr. Jenco earlier. But certainly there is a purpose in asking Syria, as American officials reportedly have been, to help ensure the safety and liberty of Terry Anderson, David Jacobsen and Thomas Sutherland now.